Mentos Geyser Science Project How to Turn the Mentos Geyser into a Great Science Project email to friend
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You might be thinking to yourself, “Can I use the MENTOS Geyser for my upcoming science project in school?” The answer is YES, but you'll need to learn how to turn a cool science activity into a real science experiment. The secret is to focus your attention away from the flying soda and concentrate on setting up an experiment where you isolate a single variable and observe the results. Tests and trials will lead you to more and more questions, which will eventually uncover a discovery. The examples below are a good starting place, but you'll stumble upon even more questions and ideas once you get started.

If you don't know how the Mentos Geyser activity works, read the experiment first.

Materials

The materials you'll need will change depending on which variables you're testing, but it's safe to say you'll need soda and Mentos® chewy mints. It's very important to use fresh soda for your experiment. Two liter bottles of soda will lose their fizz (carbonation) over time and you'll get poor results. Go to the store and buy fresh soda to get the best results.

Experiment
Video

The Fairness Factor

Before the invention of the Geyser Tube, everyone had a different method for dropping MENTOS into the bottle of soda. You might have used the test tube method while someone else made a tube out of notebook paper. Unfortunately, the method for dropping the MENTOS was never consistent. The Geyser Tube removes the inconsistency (make the drop the same every time) and lets you focus on the true variables (what you’re trying to test).

When you’re conducting the test below, you might want to remove the top cap of the Geyser Tube. This will make it easier to record how high the soda shoots up into the air because the column of soda is bigger and stays together better. Make sense?

The Scale

You want to be able to easily record how high your geyser goes. One method is to select a launching site that is up against the side of a tall building. You’ll also need an adult to help you with the next part. With permission from the owner of the building, use chalk (and an adult helper) to mark off one foot increments on the side of the building. Since you’re a scientist, it’s best to use metrics for all of your measurements.

You might want to enlist the help of another adult who own a camcorder. By recording every launch, you’ll be able to replay the tape in slow motion in order to get the best measurement possible. You see... science and technology go hand in hand.

How Many MENTOS?

It’s a question that everyone who does this project askes. What is the best number of MENTOS to use to make the highest shooting geyser? This is a great topic for a science project, but you’ll need lots of soda and MENTOS and a few friends to help record all of the data.

Let’s start with one single MENTOS. All of the bottles of soda should be the same and they should also be the same temperature. Use the Geyser Tube to make sure every launch is the same. You’ll also need a way to measure how high the soda shoots up into the air. Use a scale attached to the side of a building as one way to measure the height. It’s also a good idea to record each launch on video in order to go back and watch the launch in slow motion. Now you know your data will be accurate.

Attach the Geyser Tube to the top of the 2-liter bottle of diet soda. Push the trigger pin through the holes and load one MENTOS into the tube. You might decide not to attach the top cap – this makes it easier to record how high the soda goes because it’s not spraying everywhere. The launch site is ready... the MENTOS is loaded... the video camera is recording... and you pull the pin! Record the height (at least your best guess for right now). Repeat this same procedure for 2 MENTOS, 3 MENTOS... you get the idea. Based on your data, how many MENTOS do you need to make the highest shooting soda geyser?

The Brand Test

You guessed it... it’s time to put your favorite soda to the test. Does one brand produce higher flying geysers? How does generic soda stack up again the big name brands? Using the procedure outlined in the previous experiments, it’s easy to determine the clear winner. Remember, it’s important conduct each test the same way using the Geyser Tube and the same number of MENTOS for each launch. You’ll also want to make sure all of the soda is at the same temperature because temperature plays an important role in the reaction.

Just think... your results could help determine the next MENTOS Geyser craze.

The Temperature Test

How does the temperature of the soda affect the height of the geyser? Does a warm soda shoot up higher than a cold soda? The key to keep every launch fair and to make sure the only variable is the temperature of the soda. You’ll also need a thermometer to record the temperature of the soda just before you launch it into space.

It’s best to stick with one brand of soda for the entire test. Let’s decide to use Diet Coke. You’ll want to purchase three bottles of Diet Coke and several rolls of MENTOS. You’re going to set-up three tests: Warm soda, room temperature soda and cold soda. Place one bottle of Diet Coke in the refrigerator and let it sit over night. Place the second bottle in a place where it can reach room temperature over night. There are two safe ways to warm the bottle of soda. The simplest method is to let the unopened bottle sit in the sun for several hours. You can also place the bottle of unopened soda in a bucket of warm water. Never use a stove or microwave to heat a bottle of soda.

It’s time to return to your launching site. Check to make sure the scale is in place and the video camera is loaded with tape. Let’s start with the bottle of cold Diet Coke. Open the bottle and dip the thermometer down into the soda. Record the temperature on your data table. Attach the Geyser Tube with the trigger pin in place. Load seven MENTOS into the tube and get ready to launch. Pull the pin and record the data. Repeat the same procedure for the soda at room temperature and the warm soda.

Beyond the Fizz

Warm soda tends to fizz much more than cold soda. Why? The answer lies in the solubility of gases in liquids. The warmer the liquid, the less gas can be dissolved in that liquid. The colder the liquid, the more gas can be dissolved in that liquid. This is because as the liquid is heated, the gas within that liquid is also heated, causing the gas molecules to move faster and faster. So, they will diffuse out of the liquid, leaving less gas dissolved in that liquid. In colder liquids the gas molecules are moving very slowly, causing them to diffuse out of solution much more slowly, and more gas tends to stay in solution.

Did you know… At the bottling plant, carbon dioxide is pumped into the cans or bottles when the fluid is very cold—around 35 degrees Fahrenheit. This low temperature allows the maximum amount of carbon dioxide to dissolve in the soda.